diff --git a/blender_cloud/appdirs.py b/blender_cloud/appdirs.py
index 13485be..d1033e6 100644
--- a/blender_cloud/appdirs.py
+++ b/blender_cloud/appdirs.py
@@ -511,7 +511,7 @@ if system == "win32":
         _get_win_folder = _get_win_folder_with_pywin32
     except ImportError:
         try:
-            from ctypes import windll
+            from ctypes import windll  # type: ignore
             _get_win_folder = _get_win_folder_with_ctypes
         except ImportError:
             try:
diff --git a/blender_cloud/async_loop.py b/blender_cloud/async_loop.py
index 280e28a..2a69514 100644
--- a/blender_cloud/async_loop.py
+++ b/blender_cloud/async_loop.py
@@ -23,6 +23,7 @@ import traceback
 import concurrent.futures
 import logging
 import gc
+import typing
 
 import bpy
 
@@ -238,7 +239,7 @@ class AsyncModalOperatorMixin:
         self._stop_async_task()
         context.window_manager.event_timer_remove(self.timer)
 
-    def _new_async_task(self, async_task: asyncio.coroutine, future: asyncio.Future = None):
+    def _new_async_task(self, async_task: typing.Coroutine, future: asyncio.Future = None):
         """Stops the currently running async task, and starts another one."""
 
         self.log.debug('Setting up a new task %r, so any existing task must be stopped', async_task)
diff --git a/blender_cloud/flamenco/__init__.py b/blender_cloud/flamenco/__init__.py
index 01dd575..0e7635d 100644
--- a/blender_cloud/flamenco/__init__.py
+++ b/blender_cloud/flamenco/__init__.py
@@ -445,7 +445,8 @@ class FLAMENCO_OT_render(async_loop.AsyncModalOperatorMixin,
 
         return filepath
 
-    async def bat_pack(self, filepath: Path) -> (Path, typing.Optional[Path], typing.List[Path]):
+    async def bat_pack(self, filepath: Path) \
+            -> typing.Tuple[Path, typing.Optional[Path], typing.List[Path]]:
         """BAT-packs the blendfile to the destination directory.
 
         Returns the path of the destination blend file.
diff --git a/blender_cloud/pillar.py b/blender_cloud/pillar.py
index 5e690d5..a2482d4 100755
--- a/blender_cloud/pillar.py
+++ b/blender_cloud/pillar.py
@@ -96,18 +96,18 @@ class CloudPath(pathlib.PurePosixPath):
     def project_uuid(self) -> str:
         assert self.parts[0] == '/'
         if len(self.parts) <= 1:
-            return None
+            return ''
         return self.parts[1]
 
     @property
-    def node_uuids(self) -> list:
+    def node_uuids(self) -> tuple:
         assert self.parts[0] == '/'
         return self.parts[2:]
 
     @property
     def node_uuid(self) -> str:
         if len(self.parts) <= 2:
-            return None
+            return ''
 
         return self.parts[-1]
 
diff --git a/blender_cloud/settings_sync.py b/blender_cloud/settings_sync.py
index f0ef0bb..68f25b2 100644
--- a/blender_cloud/settings_sync.py
+++ b/blender_cloud/settings_sync.py
@@ -25,6 +25,7 @@ import functools
 import logging
 import pathlib
 import tempfile
+import typing
 import shutil
 
 import bpy
@@ -100,7 +101,7 @@ async def find_sync_group_id(home_project_id: str,
                              user_id: str,
                              blender_version: str,
                              *,
-                             may_create=True) -> str:
+                             may_create=True) -> typing.Tuple[str, str]:
     """Finds the group node in which to store sync assets.
 
     If the group node doesn't exist and may_create=True, it creates it.
@@ -122,7 +123,7 @@ async def find_sync_group_id(home_project_id: str,
 
     if not may_create and sync_group is None:
         log.info("Sync folder doesn't exist, and not creating it either.")
-        return None, None
+        return '', ''
 
     # Find/create the sub-group for the requested Blender version
     try:
@@ -144,7 +145,7 @@ async def find_sync_group_id(home_project_id: str,
     if not may_create and sub_sync_group is None:
         log.info("Sync folder for Blender version %s doesn't exist, "
                  "and not creating it either.", blender_version)
-        return sync_group['_id'], None
+        return sync_group['_id'], ''
 
     return sync_group['_id'], sub_sync_group['_id']
 
@@ -203,9 +204,9 @@ class PILLAR_OT_sync(pillar.PillarOperatorMixin,
     bl_description = 'Synchronises Blender settings with Blender Cloud'
 
     log = logging.getLogger('bpy.ops.%s' % bl_idname)
-    home_project_id = None
-    sync_group_id = None  # top-level sync group node ID
-    sync_group_versioned_id = None  # sync group node ID for the given Blender version.
+    home_project_id = ''
+    sync_group_id = ''  # top-level sync group node ID
+    sync_group_versioned_id = ''  # sync group node ID for the given Blender version.
 
     action = bpy.props.EnumProperty(
         items=[
@@ -387,12 +388,12 @@ class PILLAR_OT_sync(pillar.PillarOperatorMixin,
         """Loads files from the Pillar server."""
 
         # If the sync group node doesn't exist, offer a list of groups that do.
-        if self.sync_group_id is None:
+        if not self.sync_group_id:
             self.bss_report({'ERROR'},
                             'There are no synced Blender settings in your Blender Cloud.')
             return
 
-        if self.sync_group_versioned_id is None:
+        if not self.sync_group_versioned_id:
             self.bss_report({'ERROR'}, 'Therre are no synced Blender settings for version %s' %
                             self.blender_version)
             return
diff --git a/blender_cloud/texture_browser/__init__.py b/blender_cloud/texture_browser/__init__.py
index f7cfe51..38a9f12 100644
--- a/blender_cloud/texture_browser/__init__.py
+++ b/blender_cloud/texture_browser/__init__.py
@@ -59,17 +59,17 @@ class BlenderCloudBrowser(pillar.PillarOperatorMixin,
     project_name = ''
 
     # This contains a stack of Node objects that lead up to the currently browsed node.
-    path_stack = []
+    path_stack = []  # type: typing.List[pillarsdk.Node]
 
     # This contains a stack of MenuItem objects that lead up to the currently browsed node.
-    menu_item_stack = []
+    menu_item_stack = []  # type: typing.List[menu_item_mod.MenuItem]
 
     timer = None
     log = logging.getLogger('%s.BlenderCloudBrowser' % __name__)
 
     _menu_item_lock = threading.Lock()
-    current_display_content = []  # list of MenuItems currently displayed
-    loaded_images = set()
+    current_display_content = []  # type: typing.List[menu_item_mod.MenuItem]
+    loaded_images = set()  # type: typing.Set[str]
     thumbnails_cache = ''
     maximized_area = False
 
@@ -278,7 +278,8 @@ class BlenderCloudBrowser(pillar.PillarOperatorMixin,
         # Just make this thread-safe to be on the safe side.
         with self._menu_item_lock:
             self.current_display_content.append(menu_item)
-            self.loaded_images.add(menu_item.icon.filepath_raw)
+            if menu_item.icon is not None:
+                self.loaded_images.add(menu_item.icon.filepath_raw)
 
         self.sort_menu()
 
diff --git a/blender_cloud/utils.py b/blender_cloud/utils.py
index c32f70d..523508a 100644
--- a/blender_cloud/utils.py
+++ b/blender_cloud/utils.py
@@ -18,6 +18,7 @@
 
 import json
 import pathlib
+import typing
 
 
 def sizeof_fmt(num: int, suffix='B') -> str:
@@ -29,12 +30,12 @@ def sizeof_fmt(num: int, suffix='B') -> str:
     for unit in ['', 'Ki', 'Mi', 'Gi', 'Ti', 'Pi', 'Ei', 'Zi']:
         if abs(num) < 1024:
             return '%.1f %s%s' % (num, unit, suffix)
-        num /= 1024
+        num //= 1024
 
     return '%.1f Yi%s' % (num, suffix)
 
 
-def find_in_path(path: pathlib.Path, filename: str) -> pathlib.Path:
+def find_in_path(path: pathlib.Path, filename: str) -> typing.Optional[pathlib.Path]:
     """Performs a breadth-first search for the filename.
 
     Returns the path that contains the file, or None if not found.